Dennehy, who was 81, starred in Death of a Salesman on both Broadway and television, as well as films such as Tommy Boy, First Blood and Cocoon.

Sylvester Stallone, who performed alongside Dennehy in First Blood, shared a photo from the film on Instagram with the caption, "He simply was a brilliant performer... He also was a Vietnam vet that helped me very much building the character of Rambo."

The great actor Brian Dennehy has passed away. He simply was A brilliant performer ... He also was a Vietnam vet that helped me very much building the character of RAMBO The world has lost a great artist. #First Blood

Mia Farrow, who worked with Dennehy on the play Love Letters in 2014, shared a photo of the actor with her dog, Bowie.